We have a fluids guy on the board?
Well I design/test hydraulic systems and model pumps, motors, valves, hoses, etc in computer simulations so I guess this is my area lol. Here's my experience.
TLDR; smooth ID and as large ID as possible is taking you in the right direction.
Predicting theoretical line losses is difficult for a smooth pipe or hose, let alone a corrugated hose when using the textbook equations. There is an equation for modeling the pressure drop in a hose and an equation for modeling the pressure drop in a fitting. The hose equations don't take into account fluid temperature very well or changing of fluid direction. The equations for fittings use a fudge factor called "K" or known as bend resistivity factor. "K" is based solely on test data from various fittings at various bend angles. Sounds good but "K" is determined by one type(s) of fitting design and ran at one fluid temperature so the equations tend to fall apart in reality pretty quickly. So you often have to add an additional fudge factor of 2-3x to estimate the pressure drop. If I don't have test data, and it's a critical system, I'll perform CFD to get an idea and confirm when testing the system. Line loss is a function of the ID, length, fluid temperature, roughness of the material, and what state the flow is in (laminar, turbulent, or transitional). Changing of fluid direction (i.e. a 90 deg tight bend like a fitting) in my experience is the largest contributor to excessive pressure drop as long as the hose isn't undersized. Another thing that is often overlooked is fitting ID. Fitting I.D.'s are smaller than the hose ID and acts like an orifice. People also forget that hoses are spec'd by ID and tubes are spec'd by OD. Can't count the number of times I've spec'd out for example a -12 ID between components and come to find out it's actually closer to a -10 or -8 once the machine is built due to tubes being used instead of hoses. I've looked at enough data to know for a hose/tube operating at a "normal" fluid viscosity and smooth ID that you can represent the hose as an orifice and estimate the pressure drop using the orifice equation Flow [lpm] = Cd x Area [mm^2] x 0.000001 x sqrt(2 x pressure drop [kPa] x 1000 / fluid density [kg/m^3]) x 60000. The equation is only valid if the hose isn't saturated with flow and the pressure drop isn't rising exponentially (i.e. severely undersized hose). You can assume a smooth ID and apply the above equation to the original ID and new ID to get an idea of the % improvement, then add on the improvement you show above by switching from a corrugated hose to smooth hose.
Rule of thumb though if cost isn't an issue, smooth ID is always better, go as large as possible, and make transitions as gradual as possible to get the smallest pressure drop. I'm spec'ing out my fuel system now and I have as large of hoses and tubes as I can (within reason). I also have Bosch pressure/temp sensors at the pump outlet, FPR, and rail because I like data. Needless to say I have all 23 analog inputs used up on the standalone and need an I/O expander to get more channels. I have more money tied up in sensors than people spend on going FBO and upgraded twins it's ridiculous.
Example of various hose sizes using the orifice equation I showed above. If you have test data and know the pressure drop and flow at one point you can back calculate an effective area and extrapolate to other flows. It will follow the orifice equation curve for the most part as long as the temperature isn't changing drastically.
